1. Technical Field
The present disclosure relates to a centrifugal compressor and a turbocharger that compress suction gas by rotation of a wheel.
2. Description of the Related Art
Typically, turbochargers are known to have a shaft with a turbine wheel fitted on one end and a compressor wheel fitted on the other end and the shaft is rotatably supported by a bearing housing. The turbocharger is coupled to an engine, and the turbine wheel is rotated by the action of the exhaust gas discharged from the engine. The rotation of the turbine wheel causes the compressor wheel to rotate via the shaft. In this way, the turbocharger compresses the air by the rotation of the compressor wheel and delivers the compressed air to the engine.
The compressor wheel side of the turbocharger functions as a so-called centrifugal compressor. Generally, in a centrifugal compressor, surging occurs in an area where the suction flow rate is low. Surging occurs when the high pressure suction gas (gas) compressed by the compressor wheel flows back to an upstream side of the compressor wheel, which is the low pressure side, causing unstable behavior of the centrifugal compressor. To address this problem, the centrifugal compressor disclosed in JP S58-18600 A (Patent Literature 1) is provided with a groove (“circular groove” in Patent Literature 1) formed on the inner wall of the housing that accommodates the wheel. The groove is formed in a circular manner and extends in a circumferential direction of the compressor wheel at a position where the groove covers the leading edges of the wings of the compressor wheel. When the suction gas flown back to an area where the suction flow rate is low reaches the circular groove, the suction gas flows along the circular groove whereby the flow direction of the suction gas is changed from backflow to forward flow. This mechanism reduces the impact of the backflow of the suction gas, suppressing the occurrence of surging.